DE3125971A1 - ELECTROCHEMICAL DEVICE, SUITABLE AS A MEASURING PROBE FOR DETERMINING A GAS PRESSURE AND THE USE THEREOF - Google Patents

Description

The invention relates to a new potentiometric device, in particular as sensors or sensors (hereinafter referred to as measuring sensors) for determining the partial pressure one type of gas is suitable. In particular, it relates to a potentiometric device of the electrolyte type with reference system.

It also relates to the uses of these sensors for analyzing or determining gas, in particular for checking purposes of gaseous effluents from industrial plants or combustion gas, especially with regard to the regulation of their composition.

The potentiometric devices of the coming into imprint Art can be represented schematically as follows:

Reference system

Me, X (P ref)
Reference electrode

(A) X

JPestelek-

trolyte

X, Me ¹ (Pmes) working electrode

i.Measuring system

In this scheme, Me and Me ^{1 are} electronic conductors, A is an ionically conductive material, and X is the mobile species in the electrochemical chain.

The electrochemical reference system in contact with the electrolyte enables the generation of a partial pressure of a type of gas, which serves as a reference (pref). The working electrode, which is also in contact with the electrolyte, is located in the gas environment to be examined and consists of a material that is porous for the gases in this environment.

The presence of gaseous species in the oxidized state and in the reduced state in contact with the working electrode on the one hand and the reference electrode on the other hand results to the occurrence of a potential difference which the core see Equation suffices, according to which

τ? v _n ^ ^{ET Ln p} ref E = Eo + ^^

In this formula the symbols have the following meanings;

Eo = constant term E = electromotive force in volts R = constant for ideal gases T = temperature in degrees Kelvin

JB ¹ β Faraday number, where η represents the number of electrons that are necessary for reaction with the working electrode,

Pref = pressure of the mobile species in the frame of reference,

Pmes = pressure of the mobile species in the measuring system.

If the reference pressure and temperature are known, reading the potential enables the partial pressure to be determined the type of gas to be examined.

It is understood that for applications in large measure various gases = bar in the industry for analyzing the candidate devices and have xte efficiencies and be easy to use.

However, the devices recommended to date are sufficient for the analysis of gases does not adequately meet these requirements.

In particular, they do not allow the analysis of different gases. In addition, they generally only work

ι ί, νυ ι

at elevated temperatures. The sensors, as described in the work "Solid Electrolytes", P. Hagenmuller, W. Van Goöl, Academic Press 1978, pages 4-97, in which the ionic conductivity of zirconium is used, must be set to temperatures of the order of magnitude of 500 ⁰ C are brought.

Work carried out in the context of the invention led to the finding that it is possible to overcome the disadvantages of common known devices, overcome by using certain fluorinated anionic conductors as electrolytes can be.

Surprisingly, it was found that even with ambient or. Anionic fluorinated conductors determined at room temperature with an increased conductivity due to the 1T ~ "ion enable the determination of other species, especially such as oxygen. The investigations carried out have indeed shown that the electrical properties of a device containing this type of electrolyte be modified and that the potential that is established can be clearly seen in an advantageous manner according to the Nernst equation, which has been stated above is sufficient (it should be noted that this law is only applicable in a certain range of Pmes it is true, however, that the device under consideration can also be used outside this range).

Such a device enables measurements of To perform partial pressures of gas types that surround them.

It is therefore an object of the invention to provide a new potentiometric device useful as a electrochemical sensor for measuring partial pressures of gas types, which in particular enables measurements of to carry out different gases and this in one big one

Temperaturb © r © ieh and Tort@ilb.iLft b®i Another 2i © l the ¹ invention is di ©

of construction methods for this © sensor, those for di © into consideration

sucked application are suitable «

According to a further feature, the invention also relates to the use of these devices sur analysis of various Gases, in particular for monitoring or controlling the gaseous effluents from industrial plants or also for Investigation of the composition of gases, di © from Bxplo-

a working electrode® _9, which is porous to the gases to be examined, an adjacent electrolyte and a reference electrode, and is characterized by the fact that it contains at least one anionic fluorinated (or the corresponding osey fluoride) conductor as an electrolyte, with a conductivity that corresponds to the mobility of the HT ^ ion based, which conductor is capable of diffusion or the "dilution" of other gas species ,, in particular oxygen or oxygen ion © n ₉ so ensure that electrochemical operation of the device chains are formed in series, one of which at least one utilizes the conductivity of the üT'-Xons and a f © sten _s beaogen on S ¹ ^ ₂ constant voltage leads and of which at least one other is based diffuses on the penetration of the ion type ₉ up to a certain lows in the anioniachen conductor or dilutes (which applies in particular to the O ~ "= ion) and to a voltage as a function of that in contact with the The type of gas in the electrode ο

OI ΔΟΌ I I

The one used as an electrolyte in the device according to the invention Anionic fluorinated conductor consists advantageously of solid solutions of at least two fluorides, the fluorides with voids or defects (or the corresponding oxyfluorides).

Such solid solutions of fluorides with voids or defects are in particular of the type which forms the subject of FR patent application 2 330 127 (published). In these fluorides (or these oxyfluorides) the voids or defects result from the replacement of a first fluoride within the possible limits of solid solutions between the fluorides in question, by at least one other Fluoride which has a cation with a valence different from the first.

Such a device works in an advantageous manner starting with room or ambient temperature and does not require a heating device like the meters using zirconium, which must be brought to temperatures of the order of 500 C. she can but also either at temperatures that are below or at temperatures that are above room temperature, function.

It is also interesting to note that the materials used to make them are inexpensive and commercially available. They can be used very easily at moderate temperatures (100 ^° C.) and in an ambient atmosphere.

In addition, such a device emits a voltage which is easily measurable with less expensive devices

Parameter is. In addition, this device makes it possible to measure important voltage changes. in the In the case of oxygen, for example, changes of a few hundredths of a millivolt in the range of 10 "" Atmo are seen spheres up to the atmosphere (about 0.98 χ 10 to about 0.98 bar) solid, an area used for controlling explosion engines is particularly interesting.

According to one embodiment of the invention, the fluorides with defects or vacancies, which are used to form the electrolyte, are formed from two fluorides MF and M ¹ F and correspond to the general formula (I):

^M 1-z ^H 'z »χ ₊ . (y - χ)

where M and M 'are each a suitable cation for the formation of the fluorides with defects or vacancies and suitable effectiveness at the working temperature, the valencies χ and y of the cations being different | ζ is a number selected from a region that is a function of the cation pair M and M ⁵ and the limits of which are imposed by the limits of the possible fixed solutions between MF and M ⁸ F.

A preferred group of solid solutions with defects or vacancies of this type is formed from fluorides MF2 and M ⁰ F ₅ and corresponds to the general formula (II);

^M 1-z M ' _z F _{2 +} ζ (II)

In this formula, ζ is advantageously between 0 and 0.5 and preferably 0.20 to 0.3O ₅ and M and M 'are divalent or trivalent cations =,

3 Ί Z b 3 Υ 1

~ 12 -

Compounds of this group are, for example, fluorides with Fehlbzw. Spaces where M and M ^{1 are} Fb and Bi, respectively.

Another preferred group of solid solutions is
formed starting from fluorides MF and M ¹ F, and has the
Formula (III) on:

^U 1-z ⁿ ζ * 1 + 2z ^UJ "^L;

wherein M is a monovalent cation, M ^{1 is} a trivalent cation, and ζ represents a number from 0.50 to 0.75.

M is preferably selected from the group of Ag, Au,
Tl, Eb, K and M ¹ from the group of Bi, As or Sb.

According to a further embodiment of the invention comprises
the electrolyte is a fluoride with defects or vacancies, resulting from three fluorides MF _x , MF and M ¹¹ F with the general formula (IV): 12

where M, M ¹ and M ″ each represent a cation which is suitable for the formation of fluorides with vacancies or vacancies with sufficient conductivity at the operating temperatures} x, y _{1 and y 2 represent} the valencies of the cations, at least one this valence is different from the others;

Zy, and Zo are two numbers selected from a region which is a function of the group of cations M, M ¹ and M ¹¹ and the limits of which are imposed by the limits of the solid solutions possible between MF, M ¹ and F M "F

According to a further embodiment of the invention, the cations of the fluorides with vacancies or vacancies are selected from the group of Li ⁺ , Na ⁺ , K ⁺ Eb ⁺ , Cs ⁺ , Ag ⁺ , Tl ⁺ , Im ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , SBa ²⁺ , Cd ²⁺ , Cu ²⁺ , Zn ²⁺ , Pb ²⁺ , Sn ²⁺ , Al ³⁺ , Ga ³⁺ , In ⁵⁺ , Sc ³⁺ , Y ^{3 +} , Lanthanides (La ³⁺ to Lu ³⁺ ), Sb ³⁺ , Bi ³⁺ , Ti ⁺ , Zr, Hf, Te, I ³⁺ and preferably from the group of K ⁺ , Eb ⁺ , Cs ⁺ , Ag ⁺ , Tl ⁺ , HH ₄ ⁺ , Sr ²⁺ , Ba ²⁺ , Cd ²⁺ , Cu ²⁺ , Zn ²⁺ , Fb ²⁺ , Sn ²⁺ , La ³⁺ , Sb ³⁺ , Bi ³⁺ , Te ^{4 +} , I ⁵⁺ .

In general, the cations are selected so that the conductivity of the resulting conductor is sufficient at the temperatures of use (it is generally assumed that a conductivity is industrially useful if it is above about 10 'JI cm' at the temperature at which one wishes to work , lies).

As indicated in the aforementioned FR patent application, the fluorides with defects or vacancies advantageously have an increased conductivity per F "" ion. This conductivity can be increased by increasing the number of defects or vacancies in the anionic sublattice of the first fluoride. It can be improved further if fluorides are used which have cations with a strong polarizability, such as Tl ⁺ , Sn ²⁺ , Pb, Bi ³⁺ .

The device according to the invention can be implemented in various forms, which has a wide field of application in industry enables.

More specifically, they can be made in the form of ceramics or thin layers, or thick or dense layers.

In order to achieve the fluorinated anionic conductors used according to the invention in the form of ceramics as electrolytes ₅

J ι zoa / ι

one uses advantageously that in the FR patent application 2 330 12 7 described procedure.

It should be pointed out that a sieved mixture (preferably 100 μl or μm) of simple fluorides, which preferably contain at least one cation with strong polarizability or, better still, only cations with strong polarizability, is used. The defined product obtained is then pressed and fritted or sintered at a temperature which is sufficient for the compactness or density of the material obtained to be very high, in particular over 95 % ) or better fluorinated (e.g. HF) atmosphere to avoid any risk of hydrolysis. The working conditions are chosen so that the materials obtained have a high degree of purity.

The production of these conductors in the form of thin layers is advantageously carried out using customary deposition techniques of thin layers, advantageously according to the techniques described in published FR additional application 2 403 652 (Application 77 28113) to FR application 2 330 127 (note 75 33244) are described, the specially anionic fluorinated conductors, as mentioned above, in the structural form of thin layers.

In particular, it is possible to carry out thermal evaporation in vacuo of the fluorides, the respective cations of which correspond to the above correspond to the specified O characteristics. One can either by vaporizing the compound from a single Proceed with a crucible, or work by co-evaporation of simple fluorides, which is preferred.

In the latter case, the starting fluorides that are in the respective proportions are used that enable the formation of the desired solid solutions with defects or voids, each used in crucibles that are in a tree "in which a high vacuum is created.

The fluorides are co-evaporated by heating the respective crucibles to temperatures suitable for this purpose. The fluoride vapors formed are deposited on an insulating substrate, which is on their way is located. For certain connections it can be beneficial to heat the substrate. The deposition rate is chosen so that the thin film formed can have optimal properties5 it depends on the nature of the separated compound.

Numerous other techniques can be used to achieve deposition of fluorides with vacancies will. The expansion evaporation or flash evaporation, the electronic bombing, the cathodic or ionic sputtering, the chemical methods, etc. A description of these methods can be found for example in "Handbook of Thin Film Technology" by L. I. Moussel and R. Glang, edited by Mac Graw Hill Book Company.

Variants or adaptations of these methods or of other methods that are still known for the deposition of thinner Layers in general form can easily be found by the person skilled in the art in order to achieve solid solutions with defects or voids perform in the form of thin layers according to the invention.

ι ζ D a / ι

According to another embodiment, these arrangements are carried out in thick or dense layers, producing a paste consisting of each of the components that it is applied to canvas or a sieve using screen printing techniques, whereupon an annealing or heating process is carried out.

The choice of fluorinated anionic conductor material and the form of the potentiometric device in the state of ceramics, thin layers or thick or dense layers is carried out taking into account the experimental Conditions for the intended use.

Various factors that can easily be assessed by a person skilled in the art also play a role in this choice. Examples which may be mentioned the chemical stability of the electrolyte-forming material to a gas to be analyzed (its behavior to an oxidizing or reducing atmosphere: PBP2 'ThF ^ are advantageous, for example with an oxidizing gas and PbSnIV for effecting measurements with a reducing gas) be _f Melting point, which should of course be compatible with the experimental temperatures and, in general, the stability of the electrochemical quantities of the electrolyte (the area of electrochemical stability, i.e. the Hicht dissociation must be compatible with the voltages provided by a given reference).

The choice of this material is also influenced by the mode of implementation of the device which appears most suitable.

Thus, in the case of devising devices in the form of thin layers, it is particularly advantageous than Electrolyte to a fluorinated binary anionic conductor

and in particular to avoid the risk of dissociation.

In advantageous devices according to the invention, the reference electrode consists of a mixture of metal powder and its fluoride (Pb, PbF ₂ ; Bi, BiF ,; Sn, SnF ₂ ), its insulation being ensured by being encased in an epoxy resin. The ionically conductive materials that have already been mentioned are used in ceramic form. The working electrode consists of a thin layer of precious metal deposited by cathodic sputtering. It is advantageous to use platinum because of its catalytic effectiveness. Silver lacquer contacts (laque d ¹ argent) allow access to the electrodes.

Other characteristics and advantages of the invention result can be derived from the following description and the examples which refer to the attached figures:

Figures 1 and 2 represent construction methods for the devices according to the invention in ceramic form or in thin-film form; the figure ^ is the change curve of the voltage of a sensor as a function of the pressure of H ₂ , HF or air; Figure M- shows the change in voltage of the same probe and another probe as a function of O ₂ pressure, and Figure 5 shows the change in voltage as a function of time for three hydrogen fluoride partial pressures of a probe according to the invention.

example 1

Manufacture of a potentiometric device in the form of a ceramic: Bi, BiF ^ ZPbSnF ₂ , / Pt.

PbSnF ^ powder is placed in a closed neoprene tube with a thickness of 0.5 mm, an inner diameter of 5 && and a length of 40 mm. The PbSnF ^ is prepared in solution in water, after C. Lucat (The "se d'Etat Universite de Bordeaux I, 1980) method described. In the PbSnIV a cavity of 20 mm in length and 3 w diameter is formed. This cavity is filled with a mixture, corresponding to about 90 wt .-% bismuth as a powder and Wismuthfluorid, BiP ^ · The neoprene tube is then closed in a sealed manner. It is in one unit with isostatic pressure below 3 kb ⁰ pressure at 100 G introduced for 1 hour.

After opening the neoprene tube, a collector (collector) glued to the cover with silver lacquer. The upper part the probe is then coated with epoxy resin. Then a layer of platinum is applied to the electrolyte deposited cathodic sputtering. An electrical contact is then attached to the platinum electrode. The device is finally enclosed in a metal tube that is open at the bottom.

This device is represented by Pigur 1, in which 1 the neoprene ear, 2 PbSnIV in powder form, 3 the mixture Bi / BiF ,, 4- the collector or collector, 5 the epoxy resin, 6 the pl at in the chi cht with the electrical contact, and 9 that Represent metal pipe.

Example 2

Manufacture of a sensor in the form of superimposed thin layers

The sensor shown in Figure 2 is made by first thermal evaporation Fb (reference electrode a) is deposited on an insulating substrate d, for example glass, and then in the same Vacuum separates the electrolyte b (FbPg or FbSnF ^). The layer forming the reference electrode and the layer forming the electrolyte are covered with a protective cover e, leaving a window open where the flatin layer c is deposited. The different layers have thicknesses of 0.5 to 2 Aim or λΐ. After finished Deposition attaches the electrical connections to the electrodes.

Example 3

Investigation of the use of the devices according to the invention as measuring sensors for gas analysis

The device under investigation consists of a working electrode made of fiatin, which is porous to gas. This electrode surrounds a conductor made of fluorine ions. One uses a Material with strong ionic conductivity, such as FbSnF ^,

O 77 ' ^TiL 0 23 ♦ * 2 47 * ^ - ^ese electrolytes have ionic conductivity at room temperature due to the presence of polarizable ions such as Sn ⁺ and Fb ⁺ , and due to the presence of interstitial fluorine and vacancies, which is clearly superior to that of oxides. The conductivities measured under ambient conditions are given as examples in Table I below.

Table I.

massive thin layers

PbP ₂ ΙΟ " ⁶ -H-" ¹ cm ' ¹ 1 (T ⁵ -Π- ¹ cm- ¹

^{5 1} " ^Λ $ ¹

PbSnF ^ 10 ~ ⁵ -Π- " ¹ <ώ ~ ^Λ Λ0 ~ $ Λ." ¹ cm

A device that serves as an electrochemical reference is added to the working electrode / solid electrolyte system, using electrodes of the Fb / PbF ₂ i Sn / SnJVj >> Bi / Bii ¹ type.

The use of the sensor at around ambient or room temperature avoids certain transformations that could occur in an ionic conductor material (allotropic transformation, Conversion of the order-disorder type or orientation / disorientation, cell deformation, detachment of the electrode, if the material is not sufficiently elastic).

All measurements of the potential were carried out by means of an electrometer (type Keittley 6028) at 10 ¹ ^ SL input impedance. The temperature measurements were carried out using a thermocouple.

In the following Table II the values, calculated or measured at room temperature, are given (with respect to the electrochemical chain of the type Sn / Snl ^ / Pb ^ .. χ ¹¹ ^ ¹ ^ (Ί + χ) ^ ¹ ^ is the theoretical value with To be considered with caution, since the enthalpy of formation of SnFg is known, that of

J ^{e <iocl1 could only be} roughly estimated).

Finally, the contact results in Ag / PbSnF ^. not a priori an electromotive force (f.e.m.). However, from now on it can be assumed that the operation of the gas sensor can initiate an electrochemical imbalance that

sufficient to produce an equivalent of one battery charge.

In this Pail, two possibilities must be taken into account from the outset: the formation of Ag2 ^ ', ^{which would lead to an} electromotive force in the order of magnitude of 600 mV, or the formation of AgF, which would lead to an electromotive force of 1.27 V. .

It should be noted that these two values for the electromotive force is that which would occur if any of the silver fluorides were combined with lead fluoride.

In the last column of Table II are those obtained Voltages listed when the probe is inserted in air at atmospheric pressure at room temperature.

The following Table III relates to the test conditions and the results obtained when analyzing various types of gas, ie an oxidizing gas (C ^), a reducing gas (ILj), hydrogen fluoride gas and gaseous mixtures of HF or H ₂ in air.

Table II

Probe

ΔΗ-theoretical measured electric motor! - electromotive force ■ see force

Bi, BiP ₅

80Ö kJZMol or
200 k cal / mole

PbP ₂

-621.6 k? / Mol or -146 k calZ mol -317 mV

350-370 mV

Bi, Bi

BiP ₅

-800 kJZMol or
-200 k calZ mol

PbSnP

-124-5.3 kJZ mol or -296.5 k calZ mol -323 mV

350-370 mV

""
^

^ 0.23 * 2.47 / ^

AgZPbSnP ₄ ZPt

SnP

-623.7 kJ / mol or -915.6 kJ / mol or -148.5 k cal / mole -218 k cal / mol

AgP

PbSnP,

-185.6 kJ / mol or -1253.7 kJ / mol or -44-.2 k cal / mol -298.5 k cal / mol ^mY

-1.27 BC

- ⁶⁰ ° ^mV

50-100 mV

Table III

Probe

Bi, B

examined gas

Temperature drop ( ⁰ C)

Pressure area

110

mV / 0.98.10 " ² bar * 0.9 8 bar decade ₍₁₀ -2 _&tm> ^ ,, _{atm #)}

, 23 * 2.4-7

in air HP in air

120

25 25

" ²

38.5 mV 0.98.10

(10 ~ ² atm.

bar ■> 0.98 bar

1 atm.) 1 to 10 ⁶ ppm / air 1 to 10 ^ ppm / air

.AgZPbSnF ₄

° 2

HF

25 90 90

15 mV / 0.98.10 ~ ² * 0.98 bar 2

decade

_(1Q

-2

mV / 0.98.10 "" ² »1.27.10" ¹ bar decade _(1Q -2 ^ ₁ ^ ₁₀ -1) -17.5mV / 0.98.10 " ² ·» 0.98 bar decade

₍₁₀

-2

The Inderungskurven the voltage in the puncture with the pressure of air, HF or EU at 90 ⁰ C are shown in Figure 3 and the function of the oxygen pressure at 25 ⁰ C and 120 ⁰ C in the figure 4 ·.

In the figure 3 the change of the voltage curves are specified (at the terminal of a probe Ag / PbSnF ^ / Pt at 90 ⁰ C) in function with the pressure of the gas to be examined, or of air, HF and Ho.

In the figure M- is the change curve of the voltage as a function of the oxygen pressure on the one hand at 25 ⁰ C with a system Ag / PbSnF ^ / Pt and on the other hand at 120 ⁰ C with a system Sn-SnF ₂ / Pb ₀ ", -" TIiq 23 ^ 2

Finally, FIG. 5 relates to the kinetics of the reaction of a sensor Ag / PbSnF. / Pt as a function of the hydrogen fluoride gas pressure (at 90 C).

The overall results obtained show that the devices according to the invention are particularly suitable for analyzing various Gases are.

They are particularly useful for measuring partial pressures of oxygen in an exhaust gas from internal combustion engines and in general for controlling the combustion of hydrocarbons.

In particular, they enable analysis or determination various gases such as oxygen, hydrogen, nitrogen oxides, ammonia, fluorine, hydrogen fluoride gas and this in more advantageous Way in a wide temperature range and especially from room temperature.

The sensors according to the invention therefore enable the determination numerous polluting or explosive species, for example:

- the determination of hydrogen leaks from electrolysis units of water in pits (the detection threshold is of the order of ppm);

- the determination of fluorine gas traces in plants for isotope separation of uranium using uranium hexafluoride (the probe enables the determination of a few ppm of hydrogen fluoride gas in the atmosphere);

- the determination of NH ^, for example in cooling units.

In the case of NH, Π000 ppm NH corresponds to one in air Change of about a few tenths of a mV in the voltage of the probe.

In addition, the sensors make it possible to use materials rich in lead. This characteristic makes them of particular interest for the continuous analysis of gases that escape from explosion engines with a fuel be operated, which contains tetraethyl lead. You are not sensitive to the presence of this element, like the zirconium measuring device, which produces lead zirconate gets destroyed.

Claims (10)

AND APPROVED REPRESENTATIVES BEFORE THE EUROPEAN PATENT OFFICE DR. WALTER KRAUS DIPLOMA CHEMIST DR.-ΙΝβ. ANNEKÄTE WEISERT DIPL.-ΙΝΘ. SPECIALIZATION CHEMISTRY IRMGARDSTRASSE 15. D-BOOO MUNICH 71 · TELEPHONE O8B / 7O7O77-7B 7O78 ■ TELEX OB-2121B6 kpat d TELEGRAM CRAUS PATENT 2967 CENTER NATIONAL DE LA RECHERCHE SCIENTIFIQUE, Paris / France, Electrochemical device, suitable as a measuring sensor for determining a gas pressure and its use Patent claims M. J Elektrochemie ehe device, comprising a working electrode which is porous for gases to be analyzed, a plague electrolyte and a reference electrode, characterized in that it contains at least one fluorinated anionic conductor (or the corresponding oxyfluoride) with a conductivity based on the electrolyte Mobility of the! """Ion, this conductor being suitable for allowing the diffusion or the" dilution "of another gas species, in particular oxygen or oxygen ions, in such a way that electrochemical chains are formed in series during operation of the device at least one of which uses the conductivity of the F ~ "ion and becomes a fixed constant voltage, based on F ~ leads, and at least one other is based on the penetration of the ion species, which up to one diffuses or dilutes to a certain depth in the anionic conductor (which is particularly the case in the case of the 0 ~ - Ions applies) and leads to a voltage as a function of the type of gas that is in contact with the electrode. 2. Apparatus according to claim 1, characterized in that the fluorinated anionic conductor used consists of solid There are solutions of at least two fluorides with defects or vacancies (or the corresponding oxyfluorides), wherein the vacancies from the replacement of a first fluoride are more solid within the possible limits Solutions between the fluorides in question originate from at least one other fluoride, the one Has a cation with a valence different from that of the first. 3. Apparatus according to claim 2, characterized in that the fluorides with defects or vacancies, which are used to form the electrolyte, are formed starting from two fluorides MF and M ¹ F and correspond to the general formula I: in which M and M ¹ each represent a suitable cation for the formation of fluorides with defects or vacancies with sufficient conductivity at the operating temperatures, the valencies χ and y of these cations being different, ζ a number is selected from an area that represents a puncture of the cation pair M and M ¹ and the limits of which are imposed by the limits of the possible solid solutions between MF and M ¹ F. ^x y 4. Apparatus according to claim 3> characterized in that the solutions are formed with defects or voids, starting from fluorides MFp and M ¹ F, and correspond to the general formula II: ^M 1-z ⁿ \ * 2 ₊ z < ^I3: > wherein ζ is from 0 to 0.5 and preferably from 0.20 to 0.30 and M and M ^{1 are} divalent and trivalent cations, respectively, and in particular Pb and Bi. 5. Apparatus according to claim 3, characterized in that the solutions with voids or voids are formed starting from fluorides MF and M ¹ F, and have the general formula III: ^M 1-z ¹¹ Vi ₊₂₂ C ¹¹¹ ) where M is a monovalent cation, M ^{1 is} a trivalent cation and ζ is a number from 0.50 to 0.75, where M is advantageously selected from the group of Ag, Au, Tl, Eb, K and M ¹ from Group of Bi, As or Sb. 6 * Device according to claim 3 »characterized in that the electrolyte contains a fluoride with defects or vacancies, which consists of three fluorides MF. M ¹ F ^ and M ¹¹ F results, according to the general formula IV ^M 1 - (, ₊ Z ₂ ) " ¹ Z ₁ ^M % ₂ » χ where M, M ¹ and M "each represent a cation which is suitable for the formation of fluorides with defects or vacancies with sufficient conductivity at the operating temperatures, x, jy. and yo represent the valencies of the cations, at least one of these valencies being different from the others, Zy, and Zp are two numbers selected from a region which is a function of the group of cations M, M ¹ and M "and whose limits are imposed by the limits of the possible fixed solutions between MF, M ¹ F,« »" p are. ^y 2 7. The device according to claim 3 »characterized in that the cations of the fluorides with defects or vacancies are selected from the group of Li ⁺ , Na ⁺ , K ⁺ , Eb ⁺ , Cs ⁺ , Ag ⁺ , Tl ⁺ , MH ^ ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , SBa ²⁺ , Cd ²⁺ , Cu ²⁺ , Zn ²⁺ , Fb ²⁺ , Sn ²⁺ , Al ⁵⁺ , Ga ⁵⁺ , In ⁵⁺ , Sc ⁵⁺ , Y ³⁺ , lanthanides (La ⁵⁺ to Lu ³⁺ ), Sb ³⁺ , Bi ³⁺ , Ti ⁴⁺ , Zr ⁴⁺ , Hf ⁴⁺ , Te ⁴⁺ , I ⁵⁺ , and preferably from the group of K ⁺ , Eb ⁺ , Gs ⁺ , Ag ⁺ , Tl ⁺ , NH ⁺ , Sr ²⁺ , Ba ²⁺ , Cd ²⁺ , Cu ²⁺ , Zn ²⁺ , Pb ²⁺ , Sn ²⁺ , La ³⁺ , Sb ³⁺ , Bi ³⁺ , Te ⁴⁺ , I ⁵⁺ . 8. Device according to one of the preceding claims, in the form of thick layers, thin layers or Ceramics. 9- Device according to one of the preceding claims, characterized characterized in that the reference electrode consists of a mixture of metal and its fluoride, the electrolyte as defined in one of claims 1 to 7 and the working electrode made of a noble metal, in particular made of platinum. 10. Use of a device according to one of .Ansprüche 1 to 9 as a sensor for determining the partial pressure of a type of gas for analyzing or determining gas such as O ₂ , H ₂ , Hi ¹ or air.